The invention relates to an apparatus for dispensing small amounts of paste-like fluid from a nozzle. The invention relates more particularly to an apparatus for dispensing a predetermined volume of paste-like fluid accurately and controllably.
When forming a thick film integrated circuit on an aluminium substrate or on a heat-resisting ceramic substrate, at first the electrically conductive paste is applied by a screen process and is then fired at a high temperature, and as a next step, the resistive paste is applied by a screen process and fired at a high temperature. Such a way of manufacturing an IC(integrated circuit) hybrid is well-known. Such a conventional way of producing IC hybrids is feasible for mass-production, but a screen pattern has to be made whenever a circuit pattern is changed, and in some cases, the size of the substrate has to be changed. Accordingly, the conventional way is not feasible when producing runs of small quantities of specialty circuits. In addition, it takes a considerable amount of time to run the prototype and would cause delivery delays.
Recently, dispensing in response to a programmed computer control has been suggested. According to this suggestion, the paste is dispensed from the nozzle in response to the designed circuit information, such that the circuit is plotted directly and freely and runs of small quantities become feasible. But according to the suggestion, since the viscosity-temperature chart of the paste shows an exponential-function relation and the dispensed volume is influenced in response to the air pressure and the passage friction therein, it is very difficult to dispense the predetermined small amount of paste although air pressure is always kept constant. Further, there exists some time-delay between the air signal and the dispensed volume, and it is hard to control this timing.